Mariano Rivera, the Bronx Bomber with the responsibility of closing out the Red Sox this weekend, admits his mind is still reeling after the tragic deaths of his wife’s cousin and nephew at his Panama home.

“Even in the ballpark, there are moments when I go blank,” Rivera told The Post while preparing for last night’s battle at Fenway Park in Boston. “I try to do something so I don’t think about it.”

Rivera, whose nerves of steel are the stuff of legend, admits he’s found it impossible to concentrate purely on baseball since Tuesday, undoubtedly the most emotional day of his career.

Only hours after joining mourners at the funeral of childhood friend Victor Avila and his 14-year-old son, Victor Jr., in his tiny hometown of Puerto Caimito, Rivera made the 2,200 mile trip back to The Bronx to seal the Yankee victory in Game 1 of the American League Championship Series.

In the days following, Rivera has tried to focus on beating Boston, but his heart remained in Puerto Caimito, where his wife, Clara, stayed to mourn with her family.

Even when he was on the mound, shutting out the Sox for a second time Wednesday, he found his mind drifting back home. Each hour, he found himself picking up the phone, checking in with his loved ones.

“I’m checking in every hour – the most I can,” he shrugged on Friday, while preparing to take on the Sox in Beantown.

As his Yankee teammates swarmed around him, preparing to extinguish the dreaded Sox once again, Rivera’s father, Mariano, and mother, Delia, struggled to make sense of the tragedy.

Asked how his family was doing, he said, “As good as they can.”

Avila, who grew up with Rivera in the hardscrabble fishing village, and his son were electrocuted in a freak swimming-pool accident at the Yankee star’s mansion last Sunday.

The teen died when he jumped into the pool, unaware that it had been electrically rigged to keep two pet Rottweilers from jumping in. His father died trying to save him.

Rivera, 34, the son of a sardine fisherman, earns $10.5 million a year and spends most of his time at house in Westchester, where his three kids, aged between 2 and 9, attend school.

But he has never really left the village where he grew up dirt poor, playing baseball with gloves fashioned from cardboard and balls made from tightly wrapped fishing line and string.

Each Mother’s Day – Dec. 8 in Panama – he returns home and gathers many of the town’s moms for a party to give them kitchen appliances, televisions and furniture, family friend Michael Pinzon told The Post.

He also returns each Christmas to spread good will among his friends, many of whom live in small, cement-brick homes.

Rivera’s brother-in-law Denis Ballesteros, who was injured in the accident, acts as a live-in caretaker at the Puerto Caimito mansion, which looks over the town’s unpaved roads and back yards where roosters crow and mangy dogs wander freely.

“He’s like the man who went out to make a living and fulfilled his dream,” said Pinzon.

“He’s humble about it because he came from poverty – he came from the bottom.”

The older folks affectionately call Rivera “Pile” (pronounced pee-lee) which is a nickname an older sister gave him as a kid because she thought Mariano had too many syllables.

“I don’t think Mariano can walk around the streets of New York alone because he’d be mobbed by fans,” Pinzon said.

“Not here – it’s not unusual to see him riding his bike or walking through town like nothing.”

Rivera, known as “Mo” in the Big Apple, bankrolled the quaint Church of God of Prophesy, where he stood with tears streaming down his face Tuesday as the coffins of his loved ones passed through.

His wife, whom he began dating as a teenager almost 20 years ago, spoke to the congregation, her voice cracking. Rivera stood with his eyes closed.

“These are my cousins,” Clara said. “They are going to a better place. We should have hope.”

When tragedy struck, it was no surprise that Rivera turned his back – momentarily at least – on the most anticipated baseball series of the year to grieve with his loved ones.

“My family is my priority,” he said at the time. “I’m going to bury my cousins.”

But what stunned even his most ardent fans was that only six hours after leaving his grief-stricken hometown, he strode purposefully into Yankee Stadium ready for business.

“It was tough coming on that plane alone,” Rivera said later. “The most difficult part of my day was leaving my family, knowing that they are still in pain.”

As he took the mound in the eighth inning to the cheers of 55,000 fans, his loved ones, 2,200 miles away, also felt their spirits lift. Mourners like Pinzon, who had had been crying with Rivera hours earlier, exploded in jubilation as he struck out Boston’s Kevin Millar in the eighth and went on to nail down the win on a game-ending double-play.

“The homes here are close together, so we could hear others in the town celebrating too,” Pinzon said.